Pulse oximeters have gained rapid acceptance in a wide variety of medical applications, including surgical wards, intensive care units, general wards and home care by providing early detection of decreases in the arterial oxygen supply, reducing the risk of accidental death and injury. FIG. 1 illustrates a pulse oximetry system 100 having a sensor 110 applied to a patient 10, a monitor 160, and a patient cable 140 connecting the sensor 110 and the monitor 160. The sensor 110 has a sensor body 111 that houses emitters and a detector and is attached to a patient at a selected fleshy medium site, such as a fingertip or ear lobe. The emitters are positioned to project light of at least two wavelengths through the blood vessels and capillaries of the fleshy medium. The detector is positioned so as to detect the emitted light after absorption by the fleshy medium, including hemoglobin and other constituents of pulsatile blood flowing within the fleshy medium, and generate at least first and second intensity signals in response. The sensor 110 has a patient cable connector 114 and may have an integrated sensor cable 112. The sensor 110 may be a disposable adhesive sensor for use on a single patient or a reusable clip-on sensor for use on multiple patients.
As shown in FIG. 1, the monitor 160, which may be a standalone device or may be incorporated as a module or built-in portion of a multiparameter patient monitoring system, computes at least one physiological parameter responsive to magnitudes of the intensity signals. A monitor 160 typically provides a numerical readout of the patient's oxygen saturation 164, a numerical readout of pulse rate 166, and a display the patient's plethysmograph 168, which provides a visual display of the patient's pulse contour and pulse rate. The monitor 160 has a sensor port 162 that transmits emitter drive signals to the sensor 110 and receives the detector intensity signals from the sensor 110. The patient cable 140 provides the electrical and mechanical connection and communications link between the sensor port 162 and the sensor 110. The patient cable 140 has a sensor connector 142 that connects to the patient cable connector 114 and a monitor connector 144 that connects to the sensor port 162.